This is the first revision of a proposal by a New Investigator to look at potential genetic abnormalities that may predispose individuals to asthma. The cytokine IL-4 has been shown to be important in the development of many asthmatic lesions. IL-4 binds to the IL-4 receptor alpha (IL-4Ra). This group previously has described a novel allele of IL-4Ra in which Arg replaces glutamine at position 576. This allele, named the R576 IL-4Ra allele, correlates with a ninefold increase in atopy risk, and is also associated with increased IL-4 responsiveness. There are now at least five additional polymorphic variants of IL-4Ra, and the purpose of this application is to determine the effects of each of the IL-4Ra variants, alone and in combination, on IL-4 responsiveness and the asthmatic phenotype in humans. The applicants propose to introduce missense mutations for each of the IL-4Ra alleles into the human IL-4Ra cDNA, and to transfect them into murine B cells. They then will analyze the transfectants with respect to IL-4 sensitivity and temporal responsiveness to IL-4, specifically related to activation of STAT6 and expression of CD23. They then wish to genotype a cohort of well-characterized asthmatic patients and to identify the specific IL-4Ra alleles as markers of asthma risk or severity. Finally, they wish to look at STAT6 activation and CD23 expression in A202.1 murine B cells, as used in the first aim, after cotransfection with combinations of the different allelic variants.